Androgen receptor (AR) is an intracellular receptor having androgen such as testosterone or dihydrotestosterone as a ligand, and a DNA transcriptional regulatory protein that is activated by binding of the ligand to translocate into the nucleus (Vitam Horm, 55:309-352, 1999).
Androgen plays a key role in the establishment and maintenance of male phenotype (Vitam Horm, 43:145-196, 1986: Endocr Rev 8:1-28, 1987). That is, androgen plays an essential role in differentiation and growth of the male sexual organs, initiation and regulation of spermatogenesis, and regulation of male sexual behavior. Further, androgen also plays an important role in the development associated with virilization in the tissues other than sexual organs, such as muscle, bone, hair, larynx, skin, adipose tissue, or kidney (J Endocrinol, 126:17-25, 1990). Physiological roles of androgen in females have not been clearly revealed, but it is known that the blood level of androgen decreases with aging to cause symptoms such as lessened sexual desire and sexuality, lack of vitality, decreased sense of happiness, reduced bone mineral density in postmenopausal women, etc. (J Clin Endocrinol Metab, 81:2759-2763, 1996; J Clin Endocrinol Metab 84:1886-1892, 1999; J Steroid Biochem Mol Biol, 69:177-184, 1999). Therefore, the reduction in androgen may cause many diseases in men and women, for example, delayed puberty in boys, anaemia, osteoporosis, hereditary angioneurotic edema, endometriosis, estrogen receptor-positive breast cancer, muscle-related diseases, a decline in male reproductive ability, etc. (J Pharmocol Exp Ther, 304:1334-1340, 2003).
Current androgen replacement therapy which is a widely used therapy has effects of increasing bone density, actual weight, and sexual desire in men and women (Menopause, 13:387-396, 2006: J Clin Endocrinol Metab, 85:2839-2853, 2000: J Clin Endocrinol Metab, 85:2670-2677, 2000). However, this therapy has limitations in broad clinical trials, because of potential safety problems of androgen (N Engl J Med 350:482-492, 2004). The therapy may cause hepatotoxicity as well as severe adverse effects of prostate stimulation in men and virilism of woman
Selective androgen receptor agonists (SARM agonists) are androgen receptor ligands having tissue-selective effects, and shows positive therapeutic effects of androgen without stimulation of prostate and skin, and their oral administration is possible (J Clin Endocrinol Metab, 84:3459-3462, 1999). In other words, SARM agonists show therapeutic effects without common androgenic side effects such as prostatic hypertrophy, hirsutism, or virilism. These compounds act on androgen receptors tissue-selectively to increase their activities, thereby showing the androgenic effects while eliminating or reducing negative or unwanted androgenic properties. Accordingly, these compounds are effective in the treatment and prevention of diseases or conditions, of which symptoms may be improved or may respond to treatment by increased activities of androgen receptors, namely, disorders including those listed below:
a) symptoms associated with androgen decline in male such as sexual dysfunction, decreased sexual libido, male erectile dysfunction, hypogonadism, sarcopenia, osteopenia, osteoporosis, alterations in cognition and mood, depression, anemia, hair loss, obesity, b) symptoms associated with androgen decline in female such as sexual dysfunction, decreased sexual libido, sarcopenia, osteopenia, osteoporosis, alterations in cognition and mood, depression, anemia, hair loss, obesity, endometriosis, breast cancer, uterine cancer and ovarian cancer, c) muscle wasting disorder caused by aging, bone fracture, serious burns, end-stage renal disease, cancer, AIDS, chronic obstructive pulmonary disease, stroke, etc., and d) osteopenia and osteoporosis, muscle dystrophy caused by reduction in the number or mass of muscle cells, muscular dystrophy, post-operative muscle loss, neuromuscular disease caused by neurotransmitter system disorder, rheumatic disease, sarcopenic obesity, etc.